Windowing methods (Hamming, Hanning, Blackman) in Signal Processing - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Hamming window array

What is the output array when applying a Hamming window of length 5 using numpy?

Signal Processing

import numpy as np
np.set_printoptions(precision=4, suppress=True)
window = np.hamming(5)
print(window)

A [0.42 0.5 1. 0.5 0.42 ]

B [0.08 0.3979 0.9129 0.9129 0.3979]

C [0.08 0.54 1. 0.54 0.08 ]

D [0.0 0.5 1. 0.5 0.0 ]

💡 Hint

Recall that the Hamming window starts and ends near 0.08, not zero.

The Hamming window of length 5 produces values starting and ending near 0.08, with middle values higher. Option C matches the numpy output.

❓ data_output

intermediate

Length of Blackman window output

What is the length of the array returned by numpy.blackman when called with argument 7?

Signal Processing

import numpy as np
window = np.blackman(7)
print(len(window))

A 5

B 6

C 8

D 7

💡 Hint

The window length parameter defines the output array length exactly.

The numpy.blackman function returns an array of the exact length specified by the input argument.

🧠 Conceptual

advanced

Main difference between Hanning and Hamming windows

Which statement best describes the main difference between Hanning and Hamming windows?

A Hanning window has zero values at the edges, Hamming window has non-zero edges.

B Hamming window has zero values at the edges, Hanning window has non-zero edges.

C Both windows have zero values at the edges but differ in peak amplitude.

D Both windows have non-zero edges but differ in length.

💡 Hint

Think about the values at the start and end of each window.

The Hanning window starts and ends at zero, while the Hamming window starts and ends near 0.08, not zero.

❓ visualization

advanced

Plot comparison of Hamming, Hanning, and Blackman windows

Which option produces a plot showing all three windows of length 50 on the same graph with clear labels?

Signal Processing

import numpy as np
import matplotlib.pyplot as plt
N = 50
hamming = np.hamming(N)
hanning = np.hanning(N)
blackman = np.blackman(N)
plt.plot(hamming, label='Hamming')
plt.plot(hanning, label='Hanning')
plt.plot(blackman, label='Blackman')
plt.legend()
plt.title('Window Functions Comparison')
plt.show()

A Plots Blackman window only with incorrect title.

B Plots all three windows with labels and title correctly.

C Plots only Hamming and Hanning windows without labels.

D Plots all three windows but missing legend and title.

💡 Hint

Look for code that includes all three plots, labels, legend, and title.

Option B includes plotting all three windows with labels, legend, and title, making the visualization clear and complete.

🔧 Debug

expert

Identify error in window function usage

What error will this code raise? import numpy as np w = np.hamming(-10) print(w)

Signal Processing

import numpy as np
w = np.hamming(-10)
print(w)

A ValueError: window length must be non-negative

B SyntaxError: invalid syntax

C TypeError: unsupported operand type(s) for -: 'int' and 'str'

D No error, prints an empty array

💡 Hint

Window length cannot be negative.

Numpy raises a ValueError if the window length is negative.